In the process of testing microelectronic devices and circuits, particularly integrated circuits, such devices and circuits are routinely placed in very high vacuum environments on the order of 1.times.10.sup.-7 Torr. It is further frequently desirable to place certain components, such as multi-chip modules in a high vacuum operating environment. Such an environment is typically achieved in a high vacuum chamber. It is often necessary to communicate high frequency, high density electrical signals along a tuned impedance transmission line to such devices and circuits under test from test equipment or from other sections of an apparatus located outside the chamber. In the publication "High Frequency/High Density/High Vacuum Transmission Line Interface" by S. N. Argyrakis, one of the inventors in the present application, published Feb. 19, 1991, in CONNECTION TECHNOLOGY, the above problem is discussed in detail. As disclosed therein, when such cables are passed through the chamber wall, a potting epoxy compound is typically utilized in the feed-through area to seal the cable to the chamber wall thereby maintaining the integrity of the vacuum within the chamber. Such epoxy potting compounds typically contain entrapped gas molecules which are drawn out of the epoxy by the vacuum environment through a process called outgassing. Such outgassing has a negative impact on the productivity of the testing operation. Applicants have recognized a need for an improved technique for passing such cables through the wall of a vacuum chamber.